The technology disclosed herein generally relates to radar pulse detection. In particular, it relates to radar pulse detection using a digital radar receiver.
A receiver system is any system configured to receive energy waves and process these energy waves to identify desired information carried in the energy waves. As used herein, an “energy wave” is a disturbance that propagates through at least one medium while carrying energy. For examples, energy waves may comprise electromagnetic waves, radio waves, microwaves, sound waves or ultrasound waves.
Typically, a receiver system includes a transducer and a receiver. A transducer may be any device configured to convert one type of energy into another type of energy. The transducers used in a receiver system are typically configured to receive energy waves and convert these energy waves into an electrical signal. An antenna is one example of a transducer. A receiver processes the electrical signal generated by a transducer to obtain desired information from the electrical signal. The desired information includes information about signals carried in the energy waves.
Oftentimes, energy waves are used to carry repetitive signals. A repetitive signal is a signal that has a time period over which some aspect of the signal repeats. Repetitive signals are used in timing operations, synchronization operations, radar operations, sonar operations, and other suitable operations. For example, the characteristics of a repetitive signal may be used to synchronize two or more devices. Repetitive signals will be hereinafter referred to as -pulses”.
Digital radar receivers that detect radar signals from other radars have front-end receivers that produce pulse descriptor words (PDWs) for each radar pulse they detect. They are unlike radar systems in that they do not naturally produce range and they must handle unknown signals rather than look for reflected versions of their transmitted signals. The digital versions of these receivers are typically designed as a channelizer or filter bank; within each filter channel, radar pulses are separated from other coincident signals and have their noise decreased by the relative filter bandwidth compared to the total input bandwidth. These pulses with their increased signal-to-noise ratio (SNR) are processed to generate data representative of estimated signal characteristics of interest, such as phase modulation parameters, frequency, bandwidth, time of arrival, time of departure, pulse width, pulse amplitude, pulse repetition interval, and/or angle of arrival. While such channelizers have many advantages, they also have key disadvantages such as large size, weight and power that come from all the multipliers and adders required for very large filter banks that must operate continuously whether a signal is present or not. In addition, signals that do not match the bandwidth and frequency of each filter in the filter bank are processed sub-optimally or split across filter channels, resulting in missed, false and inaccurate PDWs. If a channelizer is not used, the two main processing tasks of noise reduction and signal separation must be done using different methods. In either case, separated signals must be processed for PDW information for each received pulse. In order to achieve reliable PDW processing, there must be reliable pulse detection.
Existing solutions to pulse detection rely on threshold crossing as the main method of detection. Thus, this approach limits the processing of pulses to those with relatively high signal-to-noise ratio (pulses that are easily distinguishable from the noise). This in turn limits the detection range of any receiver that uses the threshold technique (unless the transmitter signal power is increased).